Did this ever happen to Redd Foxx?
During a break from rehearsals on October 11, 1991, a fatal heart attack felled him on the set. Reportedly, Reese and the rest of the cast and crew thought he was doing his classic (and in this case, ironic) "I'm coming, Elizabeth" fake heart attack routine he made famous on Sanford and Son, even going as far as collapsing to the floor, although that was not part of the usual schtick.[3] However, this heart attack was real, and Foxx never regained consciousness.
I believe that this did actually happen to actor/commedian Dick Shawn, who died while on stage during a standup comedy act.
From Wikipedia:
Foxx appeared to be making a comeback with the 1991 series The Royal Family, in which he co-starred with his long-time friend Della Reese. During a break from rehearsals on October 11, 1991, a fatal heart attack felled him on the set. Reportedly, Reese and the rest of the cast and crew thought he was doing his classic (and in this case, ironic) “I’m coming, Elizabeth” fake heart attack routine he made famous on Sanford and Son, even going as far as collapsing to the floor, although that was not part of the usual schtick.[3] However, this heart attack was real, and Foxx never regained consciousness. He was 68 years old.
Actually yes, it did.